This invention relates to a holding element for fastening components to a carrier, and particularly relates to a holding element for fastening components to a carrier which is formed with an opening.
As shown in European Patent Application No. 890 750 A2, a known holding element, which is to be assembled with a carrier, is constructed integrally in the manner of a plug. The holding element is formed with a shank and a flange, at one end of the shank, and a bore which extends axially through the flange and into the shank. A bead is formed on the shank and is spaced from the flange. The distance between the bead and a spaced facing portion of the flange corresponds to the thickness of the respective carrier.
When assembling the holding element with the carrier, the shank is placed through an opening in the carrier, with the flange engaging one side of the carrier. As the holding element is being assembled with the carrier, the bead is compressed as it passes through the opening of the carrier, and then returns to its normal uncompressed state as the bead clears the opening. In this manner, the portion of the carrier which surrounds the opening thereof is, in effect, captured between the flange and the bead. A screw is then inserted through an opening formed in a component which is to be assembled with the carrier. The threaded portion of the screw is threadedly assembled within the bore of the holding element. During the threaded assembling of the screw, the screw exerts a radially outward pressure against the portion of the shank which is contained within the opening of the carrier, thereby providing a tight seal against the wall of the opening. Also, the head of the screw presses the component against the flange, to complete the assembly of the component with the carrier.
In order to firmly support the screw within the bore of the holding element, the elasticity of the material of the shank must not be too soft. In order to provide for the compression of the bead as the holding element is being assembled with the carrier, the region of the bead should be a soft material. However, a soft material would not provide adequate support for the screw.
Thus, there is a need for a holding element, used for mounting a component with a carrier, which provides sufficient material compressibility for easy assembly of the holding element with the carrier, and sufficient material strength to facilitate firm assembly of a screw with the holding element.
It is, therefore, an object of this invention to provide a holding element which may be easily assembled on a carrier, yet provide high stability for the mounting of a screw therewith, thereby providing good support function for a component to be fastened with the carrier, and guaranteeing secure mounting and sealing of the holding element with the carrier.
With this and other objects in mind, this invention contemplates a holding element for fastening components to a carrier formed with an opening, in which the holding element is to be inserted and held. The holding element includes an insertion piece, which is insertable into the opening of the carrier, and which has a longitudinal insertion-piece bore extending therethrough. The insertion piece is formed with a collar at one end, which collar is to be supported against the carrier, and an insertion-piece thrust face formed at another end of the insertion piece. A thrust part is formed with a thrust-part longitudinal bore having an open end and a thrust-part thrust face formed adjacent the open end of the thrust-part bore. The insertion-piece thrust face and the thrust-part thrust face are in interfacing engagement, with the insertion-piece bore being in axial alignment with the thrust-part bore. The insertion piece is made of a soft elastic plastics material, and the thrust part is made of a material having the stability of a rigid plastics material, which is more rigid than the soft elastic plastics material of the insertion piece. When a screw is inserted through the insertion-piece bore and into the thrust-part bore, the insertion piece is compressed to expand within the opening of the carrier in a sealing manner to anchor the holding element with the carrier.
The two-piece construction of the holding element, and the matching configuration of the thrust faces of the insertion piece and the thrust part result, on the one hand, in ease of assembly because there is no need to provide a bead or the like on the insertion piece due to the compressive expansion of the insertion piece by the thrust part. Thus, the external contour of the holding element may be substantially smooth, thereby allowing it to be inserted into the opening of the carrier without difficulty. When the screw is tightened within the bores, the rigid thrust part is drawn or pressed against the softer insertion piece in the region of the matching thrust faces. This results in a strong radial pressure being applied to the insertion piece to snugly secure the insertion piece against the wall of the opening of the carrier to provide a reliable seal. The soft elasticity of the insertion piece does not impair the tight fit of the screw with the holding element because the screw is inserted into the rigid thrust part, with the result that a component pressed against the holding element by the screw may be attached securely and firmly to the carrier by the holding element.
The thrust face of the insertion piece is formed with a conical surface which is contiguous with the longitudinal bore in a direction away from the collar. The thrust face of the thrust part is formed with a cone surface, which is in interfacing and complimentary engagement with the thrust face of the insertion piece. When the screw is tightened, the thrust face of the rigid thrust part is pressed against the thrust face of the softer insertion piece, which compresses the insertion piece to expand radially outward against the wall of the opening of the carrier.
An elastic ring may be formed on the insertion piece, between the collar and the thrust part, which embraces a collar of the thrust part projecting into the ring. With such construction, the collar ensures that, when the elastic ring is compressed as a result of tightening the screw, the ring may expand only radially outward where it then presses against the wall of the opening of the carrier.
The collar of the insertion piece is designed in the shape of a dish, with a marginal lip around the periphery of the dish being positioned for application against the carrier when the insertion piece is assembled with the opening of the carrier. The dish configuration gives rise, on the one hand, to an efficient sealing between the holding element and the carrier and, on the other hand, to a stable abutment relative to the component to be fastened, and pressed toward the collar of the insertion piece by the screw.
In order to achieve retention of the insertion piece with the thrust part when forming the holding element, the insertion piece is connected to the thrust part by elastically deformable ribs. The ribs may be provided at random points in the region of contact between the insertion piece and the thrust part, such as, for example, at the outer edge of the cone surface of the thrust part. The ribs may be injection-molded onto the insertion piece and the thrust part.
The insertion piece and the thrust part are injection molded from plastics materials and, as stated above, a particularly elastic plastics material is to be selected for the insertion piece. During injection-molding of the holding element, both the extremely elastic insertion piece and the comparatively more rigid thrust part may be formed in one mold, in which case the ribs connecting the insertion piece and the thrust part may be molded in place at the same time.
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiment, the appended claims and the accompanying drawings.